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Method for producing electrode material for lithium ion batteries

a lithium ion battery and electrode material technology, applied in the field of graphite material, can solve the problems of increasing power consumption, affecting the performance of electrodes, affecting the cycle life of electrodes, etc., and achieves the effects of low cost, good product quality, and excellent stability

Inactive Publication Date: 2015-06-16
SHOWA DENKO KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a method for producing a high-quality graphite material that is stable, has low impurities, and is cost-effective. This material is useful as an electrode material for lithium ion batteries. When used as a negative electrode, the material allows for smoother insertion and release of lithium ions, resulting in superior battery performance in terms of input-output characteristics and cycle lifetime.

Problems solved by technology

The function of the mobile device or the like is diversified, resulting in increasing in power consumption thereof.
In particular, in applications for automobiles, such as battery electric vehicles (BEV) and hybrid electric vehicles (HEV), a long-term cycle characteristic over 10 years and a large current load characteristic for driving a high-power motor are mainly required, and a high volume energy density is also required for extending a driving distance, which are severe as compared to mobile applications.
When an electrode made of such a material is charged, the electrode expands only in one direction, which degrades the performance of the electrode such as current characteristics and cycle life.
Further, as a demerit of high crystallinity, the surface of the natural graphite is active, and hence a large amount of gas is generated during initial charging, which decreases an initial efficiency and further degrades a cycle life.
However, it is very difficult for the material to satisfy the requests such as a large current and an ultralong-term cycle characteristic of a large battery as described above.
In addition, natural graphite has a problem relating to quality stability because it contains a large amount of metallic impurities such as iron.
However, it is difficult to achieve the cycle characteristics for a long period of time which are required for a large battery due to problems such that the conductive contact of the electrode powder with each other tends to degrade.

Method used

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  • Method for producing electrode material for lithium ion batteries
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Examples

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example 1

[0168]A petroleum-based raw coke (non-needle coke) whose heating loss measured by thermogravimetry (TG) in the range of 300° C. to 1,200° C. was 12.5 mass % was treated at 1200° C. with a Roller Hearth Kiln manufactured by NGK INSULATORS, LTD. while a nitrogen gas was supplied. Next, the resultant was pulverized with a Bantam Mill manufactured by Hosokawa Micron Corporation. The pulverized product was subjected to air classification with a Turbo Classifier manufactured by NISSHIN ENGINEERING INC. to obtain a carbon material 1 having a D50 value of 20.0 μm. Carbon material 1 had a compact powder resistivity of 0.25 Ω·cm when compressed to a density of 1.4 g / cm3, and had an angle of repose of 36°.

[0169]A furnace having a vertical length of 500 mm, a horizontal length of 1,000 mm, and a depth of 200 mm was made of ceramic bricks, and then electrode plates each measuring 450 mm long by 180 mm wide by 20 mm thick were placed on both end surfaces inside the furnace. Carbon material 1 was ...

example 2

[0175]Carbon material 1 having a D50 value of 19.0 μm was obtained by the same operations as those of Example 1 except that the same petroleum-based raw coke (non-needle coke) as that of Example 1 and a petroleum-based raw needle coke whose heating loss measured by TG in the range of 300° C. to 1,200° C. was 11.5 mass % were mixed at 1:1 and used as an organic carbon material.

[0176]Carbon material 1 had a compact powder resistivity of 0.20 Ω·cm when compressed to a density of 1.4 g / cm3, and had an angle of repose of 42°.

[0177]Carbon material 1 was graphitized by the same method as that of Example 1. Table 1 summarizes the various physical properties and battery evaluation results of the resultant graphite material (carbon material 2) together with the physical properties of the organic carbon raw material and carbon material 1. As compared with Example 1, the d002 was small and the capacity was high, but the initial efficiency was somewhat low.

example 3

[0178]A graphite material (carbon material 2) was obtained by the same operations as those of Example 1 except that 1,000 ppm by mass of B4C were added at the time of the graphitization. Table 1 summarizes the various physical properties and battery evaluation results of the resultant graphite material (carbon material 2) together with the physical properties of the organic carbon raw material and carbon material 1. As compared with Example 1, the d002 was small and the capacity was high as a result of the addition of a graphitization co-catalyst, but the initial efficiency was somewhat low.

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Abstract

A method for producing a graphite material for lithium ion batteries, including a step for exothermically graphitizing a carbon material by directly applying an electric current therethrough. The carbon material is obtained by heating at a temperature in the range of 800° C.-1500° C. inclusive and subsequently pulverizing an organic carbon starting material, has a compact powder resistivity of 0.3 Ω cm or less when compressed to a density of 1.4 g / cm3, has an angle of repose in the range of 20° to 50° inclusive, and has a particle size (D90) in the volume-based particle size distribution measured using laser diffraction of 120 μm or less. The average surface interval (d002) of a surface (002) of the carbon material after graphitization, measured using x-ray diffraction, is in the range of 0.3354 nm-0.3450 nm inclusive.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a National Stage of International Application No. PCT / JP2012 / 077038, filed Oct. 19, 2012, claiming priority from Japanese Patent Application No. 2011-232291, filed Oct. 21, 2011, the contents of all of which are incorporated herein by reference in their entirety.TECHNICAL FIELD[0002]The present invention relates to a graphite material.BACKGROUND ART[0003]As a power source of a mobile device, a lithium ion secondary battery is mainly used for the reason of its high-energy density and long cycle life. The function of the mobile device or the like is diversified, resulting in increasing in power consumption thereof. Therefore, a lithium ion secondary battery is required to have an increased energy capacity and, simultaneously, to have an enhanced charge / discharge cycle characteristic. Further, there is an increasing demand recently for a secondary battery with a high output and a large capacity for electric tools such as ...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): H01M4/587C01B31/04H01M10/0525
CPCH01M4/587C01B31/04H01M10/0525Y02T10/7011C01B32/20C01B32/205Y02E60/10C01P2002/78C01P2006/40C01P2004/61
Inventor WAKIZAKA, YASUAKIKAMIJOU, YUUICHITAKEUCHI, MASATAKANISHIMURA, YOSHIYUKIMIURA, RYUSUKEFUKAI, TAKAYUKI
Owner SHOWA DENKO KK